The ball visual also works for raw or cooked vegetables. One serving of cooked veggies, such as carrots or broccoli, is a 1/2-cup, or about the size of a tennis ball. One serving of leafy greens is equal to one full cup, equal to a man’s fist, while the salad dressing you put on those greens should be equal to just 3/4 of a shot glass, Beauvais says. Aim for at least 21/2 cups of vegetables a day for a healthy weight-loss diet.